1. Field of the Invention
The present invention relates to a high speed-perforating apparatus which bores annular holes in a material to be perforated comprising a concrete structure at high speed, for example, when anchors and the like are set up for the post-construction of the concrete structure.
The present specification is based on Japanese patent applications (No. HEI 11-301753, HEI 2000-049943, HEI 2000-176035) and the contents of these applications are incorporated herein.
2. Description of the Related Art
For strengthening an existing wall made of concrete, the following method is known: first, a hole having a large size is made in the wall to provide an opening; next, a brace (diagonal brace) made of iron is provided in the opening thus made; and then the brace and anchors disposed in the inward peripheral face of the opening are consolidated with concrete, to thereby strengthen all over wall. In this case, each anchor is received in a hole arranged in the inward peripheral face and set up therein.
The hole for setting up an anchor is formed by using an apparatus which comprises a core bit 80 having an annular bit 80a composed of diamond tip, cemented carbide tip or the like in the end of a cylindrical member, and a motor 81 for rotating the core bit 80 around the axis thereof, as shown in FIG. 9.
Namely, a core 83 having a columnar shape is formed by rotating the bit 80a provided in the end of the core bit 80 while the bit 80a is pressed against a concrete 82 to be perforated therein, followed by pulling out the core bit 80 from the inside of the concrete 82.
Then, the core 83 left in the inside of the concrete 82 is pulled out after breaking off the root thereof, whereby a hole having, for example, a degree of size-a diameter of 20 to 35 mm and a depth of 200 mm is formed for setting up an anchor.
In the above-mentioned apparatus, the motor 81 is heavy and lack of easy handling as in engines oil-hydraulic motors, or the like, because the motor 81 comprises gears through which the core bit 80 is rotated. In addition, the apparatus has a problem in generating a big noise (more than 90 dB). Further the apparatus has problems in that the number of revolution is as low as about 1500 rpm even at high speed and a maximum number of revolution is a degree of 3000 to 3900 rpm even in the case of special electric motors, whereby it takes a long time to perforate.
Ultrasonic perforating apparatus which perforate by ultrasonics can perforate with a comparatively low noise and on the other hand the perforating speed thereof is slow, to thereby take a long time to perforate as in the case of the above-mentioned apparatus having a motor.
Though a perforating time can be shortened by thinning the cutting edge thickness of the bit 80a of the core bit 80, there is a problem in that a tool load imposed on the bit 80a is increased and a force directed to a perforating direction (normal force) is increased, both due to thinning the cutting edge thickness, to thereby bring out the buckling of the core bit 80.
Accordingly, an object of the present invention is to provide a high-speed perforating apparatus which can perforates within a short time at a high revolution without buckling a core bit attached thereto, accompanied by a low noise.
The high-speed perforating apparatus of the present invention comprises a cylindrical core bit having a bit for boring an annular hole in a material to be perforated and a motor having a cylindrical stator disposed around the outer periphery of a cylindrical rotor into and through which a rotary shaft is inserted and to which the same is fixed, wherein the core bit is directly attached to the rotary shaft of the motor without transmission means such as gear, belt or the like and is directly rotated at high speed by the motor.
Accordingly, in the high-speed perforating apparatus of the present invention, a perforating speed can be greatly increased, as compared with the conventional apparatus which perforates at low speed.
Thereby, working for perforation can be rapidly carried out to shorten terms for various construction works having perforating works.
Further, in the high-speed perforating apparatus of the present invention, noise can be greatly reduced (about 70 dB) and as the number of parts are small, labors necessary for maintenance works can be greatly reduced, as compared with engines, oil-hydraulic motors and electric motors having gears.
As mentioned above, a tool load imposed on a bit can be decreased by rotating a core bit at high speed, whereby even when the cutting edge thickness of the bit is thin, a normal force which is directed to a perforating direction can be small, perforation can be smoothly carried out without troubles such as buckling while always maintaining a good cutting performance, and a perforating time can be reduced.
The method for a high-speed perforation of the present invention comprises the steps of: providing for a motor having a cylindrical rotor into and through which a rotary shaft is inserted and to which the same is fixed and having a cylindrical stator disposed around the outer periphery of the cylindrical rotor; attaching directly to the rotary shaft of the motor a cylindrical core bit having a bit for boring an annular hole in a material to be perforated without transmission means such as gear, belt or the like; and rotating directly the core bit at high speed by rotating the rotary shaft, to thereby bore a hole in the material to be perforated with the bit.
Accordingly, a perforating speed can be greatly increased, as compared with the conventional perforating method carried out at low speed.
Whereby, working for perforation can be rapidly carried out to shorten terms for various construction works having perforating works.
Further, in the method for a high-speed perforation of the present invention, noise can be greatly reduced (about 70 dB) and as the number of parts are small, labors necessary for maintenance works can be greatly reduced, as compared with engines, oil-hydraulic motors and electric motors having gears.
As mentioned above, a tool load imposed on a bit can be decreased by rotating a core bit at high speed, whereby even when a bit having a thin cutting edge thickness is used, a normal force which is directed to a perforating direction can be small, perforation can be smoothly carried out without troubles such as buckling while always maintaining a good cutting performance and a perforating time can be reduced.